Hardened Portland Cement Paste Research Articles

Effect of curing conditions on the total water content of hardened portland cement paste

AbstractThe effect of various curing conditions on the amount of water held by pastes with low water/cement ratios was investigated. It was concluded from the results that factors significantly influencing the total water content of a cement paste made with ordinary Portland cement and cured at room temperature are: water/cement ratio, curing medium, curing period and curing history.

Mechanism of the carbonatation shrinkage of lime and hydrated cement

AbstractCarbonatation of hydrated lime compacts produces shrinkage and changes in mechanical properties comparable with those found in similarly treated compacts of bottle‐hydrated cement and samples of hardened Portland cement paste. From experimental results obtained with the simpler lime system a mechanism for carbonatation shrinkage is proposed that postulates a through‐solution reaction and induced cycles of wetting and drying.Experiments on compacts of bottle‐hydrated cement show that carbonatation of the ‘combined lime’ is at least as rapid and extensive as the carbonatation of the ‘free lime,’ and that contrary to current opinion the former reaction results in even greater carbonatation shrinkage. The mechanism for carbonatation shrinkage of this system is considered to be connected with dehydration and polymerisation of the hydrous silica product of carbonatation.

A note on the occurrence of crystals of calcium hydroxide and ettringite in voids in hardened Portland cement paste

Summary The occurrence of crystals of calcium hydroxide and of ettringite (calcium sulphoaluminate) in hardened Portland cement, reported previously by others, is confirmed. Samples of hardened Portland cement paste prepared half a century ago at one of Canada's earliest cement plants were, on examination, found to contain voids in which well developed crystals had formed. The crystals occurred as thin plates and needles that were identified by optical microscopy and X-ray diffraction as calcium hydroxide and ettringite, respectively. It is of interest that the calcium hydroxide had not been altered to carbonate even though the cement samples had been stored for a long time under conditions that would be expected to promote this change.

Porosity of Hardened Portland Cement Paste

Porosity of Hardened Portland Cement Paste

Reaction of hardened portland cement paste with carbon dioxide

Reaction of hardened portland cement paste with carbon dioxide

The effect of moisture on the dielectric constant of hardened portland cement paste

Measurements are reported of the dielectric constant of hardened portland cement paste as a function of water content between 0.1 and 10 MHz and at microwave frequencies at 3000, 3750, 7450 and 9375 MHz. The dielectric losses observed seem to be conductivity losses (capillary water, adsorbed water) at the lower frequencies, whereas at microwaves they seem to be due primarily to the relaxation of the free or capillary water in the pores.

Structure and Physical Properties of Hardened Portland Cement Paste

Methods of studying the submicroscopic structure of Portland cement paste are described, and deductions about structure are presented. The main component, cement gel, is deposited in water‐filled space within the visible boundaries of a body of paste. Space filled with gel contains gel pores; space not filled by gel or other solid material is capillary space. Hygroscopicity of cement gel, and capillary pores, accounts for various aspects of the properties and behavior of concrete. Data on gel and paste structure are used in discussing strength, permeability, volume stability, and action of frost.

Specific Volume of Evaporable Water in Hardened Portland Cement Pastes

Specific Volume of Evaporable Water in Hardened Portland Cement Pastes

Porosity of Hardened Portland Cement Pastes

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Studies of the Physical Properties of Hardened Portland Cement Paste

Studies of the Physical Properties of Hardened Portland Cement Paste

Studies of the Physical Properties of Hardened Portland Cement Paste

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Studies of the Physical Properties of Hardened Portland Cement Paste

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Studies of the Physical Properties of Hardened Portland Cement Paste

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Studies of the Physical Properties of Hardened Portland Cement Paste

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Studies of the Physical Properties of Hardened Portland Cement Paste

Studies of the Physical Properties of Hardened Portland Cement Paste

Studies of the Physical Properties of Hardened Portland Cement Paste

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